Occupational Solar Ultraviolet Radiation and Breast Cancer Risk
UVR , Solar UVR , occupation , breast cancer
Background: Solar ultraviolet radiation (UVR) has potential protective and confirmed detrimental effects on cancer risk. Several studies have examined recreational sun exposure in relation to breast cancer risk, and a recent meta-analysis found that moderate sun exposure (1 to <2 hours/day) was associated with a decreased risk of breast cancer. Only one previous study in Canada has investigated sun exposure and breast cancer risk in an occupational setting. The objectives of the present study were to investigate the relationship between occupational solar UVR and breast cancer risk in Canada. Methods: A case-cohort study was conducted utilizing data from the Canadian Partnership for Tomorrow's Health (CanPath) prospective cohort study. Questionnaires were completed at baseline to obtain information on sun exposure, current and longest job held, and breast cancer risk factors. Cancer outcomes were ascertained via linkage with provincial cancer registries and administrative databases. Longest held job at baseline was linked to a job exposure matrix to assign exposure to occupational solar UVR. Breast cancer risk estimates (hazard ratios [HR]) and 95% confidence intervals were estimated using a weighted Cox proportional hazard’s regression model with age as the timescale. Results: A total of 1,822 breast cancer cases met eligibility criteria from the underlying cohort and a random sample of 7,361 female participants were selected for the subcohort. The prevalence of occupational exposure to solar UVR was 2.2% in the case-cohort. HRs (1.14 (95% CI 0.84-1.54)] do not suggest that occupational solar UVR has a protective or detrimental effect on the risk of breast cancer for Canadian females. When analyzed by menopausal status, the risk for pre-menopausal breast cancer was elevated, but not statistically significant (HR=1.66 [95% CI 0.93-.95]). Occupational solar UVR was not associated with the risk of breast cancer for post-menopausal Canadian females. Conclusion: Previous research has focused on recreational sun exposure. The present study is the second to examine the relationship between occupational sun exposure and breast cancer in Canada and suggests that occupational exposure to UVR, may increase breast cancer risk in pre-menopausal females.